title: Light-induced excited spin state trapping and charge transfer in trigonal bipyramidal cyanide-bridged complexes.
abstract: Three members of the family of trigonal bipyramidal (TBP) complexes of general formula [M(tmphen)(2)](3)[M'(CN)(6)](2) (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline) or [M(3)M'(2)], which are known to exhibit thermally induced spin crossover and charge transfer, have been investigated for optical and photomagnetic properties. The light-induced excited spin-state trapping (LIESST) effect found in classical spin crossover compounds, such as [Fe(phen)(2)(NCS)(2)], was explored for the [Fe(3)Fe(2)] and [Fe(3)Co(2)] compounds. Similarly, inspired by the light-induced charge-transfer properties of K(0.2)Co(1.4)[Fe(CN)(6)]·6.9H(2)O and related Prussian blue materials, the possibility of photo-induced magnetic changes was investigated for the [Co(3)Fe(2)] TBP complex. Optical reflectivity and magnetic susceptibility measurements were used to evaluate the photoactivity of these compounds. A comparison of these data before and after light irradiation demonstrates that (i) the spin crossover of the Fe(II) centers in the [Fe(3)Fe(2)] and [Fe(3)Co(2)] analogues and the (ii) charge transfer events in the [Co(3)Fe(2)] complex occur with temperature and irradiation. In addition, photomagnetic behavior is exhibited by all three compounds. The photo-conversion efficiency has been estimated at 20% of photo-induced high spin Fe(II) centers in [Fe(3)Co(2)], 30% of paramagnetic Co(II)-Fe(III) pairs in [Co(3)Fe(2)], and less than 2% of photo-induced high spin Fe(II) centers in [Fe(3)Fe(2)].
authors.affiliation: Department of Chemistry, Texas A&M University, College Station, Texas 77842, USA.
authors.forename: Kristen E
authors.initials: KE
authors.lastname: Funck
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Prosvirin
authors.forename: Corine
authors.initials: C
authors.lastname: Mathonière
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Clérac
authors.forename: Kim R
authors.initials: KR
authors.lastname: Dunbar
mesh_terms: D018360:Crystallography, X-Ray; D008027:Light; D008958:Models, Molecular; D009570:Nitriles / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D009570:Nitriles; D009942:Organometallic Compounds